what is causing this?

i have a 1999 polaris xlt sp (600 triple) and it is doing a very odd thing. when i drive in a field in a track that is already made the machine seems to work fine and has a fair amount of power, yet when i am making my own track in the snow the machine slowly boggs until it no longer has enough power to pull it self and dies, i can start it and pick up the back end and spin the track then it will drive away, i have cleaned the clutches and the clearences seems ok for not being rebuilt(the drive has #10 weights and the driven is on the second setting, it seems to shift very early), another thing it does is when i start it cold it will idle at 35-3850 rpm then idle down to 2000rpm, then when i ride for a while (hard, half to full throttle) then let off rapidly it will idle then a minute later it will die, i have had the bowls off and cleaned all the jets(it has the three carbs that are linked together by rods, they have three air screws but only one idle screw), i am also running UNI foam filters(not oiled)

can anyone give me an idea on either of my problems thanks

Sound like it is over fueling. Is it hard to start? Is the jetting correct for the altitude? Do you have an altitude sensing carb system (ACCS)? Have you check your needle and seats in the carbs?

it is easy to start cold 3-4 pulls on full choke, and one pull when warm, except when it bogges then i have to give the throttle a little pressure, it is jetted to factor and the needles and seats are not stuck

i am in saskatchewan, saskatoon to prince albert very flat

Stick the airbox back on there, probably loading up with fuel under load.

Well there I was....

A few years back, I posted about my 600 XCR having near identical problems. I was told to look in many places, but 2 stick out. I was bogging and had a crank bearing seal leak on the PTO end, and getting power was hit and miss. By the time I discovered the culprit, I had burned down a piston (PTO) I believe. The choke cable has 3 lenghts to it and runs about $50 brand new, but after time, the cables do not wear or lengthen uniformly, and so the easiest fix is to install a new one. And sense you're there and will be adjusting the chokes, go through the carbs again. Each choke adjusts individually, so remember to set them all exactly alike, because this is how your air is metered (during choking) for your fuel ratio. If you reuse the old cable, it will have a tendency to stretch and play some more, and this really becomes the issue when you are NOT choked.
After the machine warms up, the stetched cylinder cable may not be fully closed, inadvertently choking one cylinder and not the others. This in turn enrichens the mixture ratio in that cylinder which may lead to preignition simply because of the amount of unburned fuel through each compresion cycle builds up and continues to generate excess heat.
Take a good close look at the choke cable and how each one meters to the individual carbs and make sure that they are the same, do a compression check, and also if you have it available,(borescope) try to get a look down in each cylinder and look for pitting or uneven combustion wear patterns.
Good Luck!

sounds like a fuel delivery problem to me - works when its not loaded fully in a track, doesnt work when in fresh making tracks. one uses much more horspower and fuel than the other so....

check the simple things first.

1) DO THIS AND DONT FORGET TO DO IT>check the tank breather line. if it is plugged the tank winds up in a vaccume (make sure it is not kinked) a buddy ate 2 motors before we found this little gem of a problem. its the clear little tube that crosses the steering column. just take the gas cap off and blow in the little tube. it should transfer air easily. I check mine regularly.

2) check fuel filters what i mean is replace the fuel filter or eliminate it all together (I never had a problem)

3) check the fuel pump. I really donnt know how to check it other than removing the carb feed lines and starting it and having fuel squirt like crazy (very dangerous) ya know spark plugs and electricity and heat.


I think one of these is your culprit
spomey

thanks for the info on your engine burning and that i should put the air box back in it is just the air box has no mounting hardware so it is all lose which means that the cdi is not held down which i fixed right of way, also i will replace that seal and the choke cables, how hard is it to replace the crank seal, and also how hard is it to take the carbs all a part and then set them up again, there are pics of this carb on www.rallypa.com under the left hand column is a parts fiche thanks

When you had the secondary apart, did you preload the spring/helix by 1/3 of a rotation or just push the helix over the keyway?? Sounds like no tortional preload on the secondary spring to me. Very common.

I would check you carb settings yourself. I bought a used sled a few years back that would backfire downstop. Dealer went through the carbs TWICE and couldn't find the problem. I took it home and checked the main jets and they were the wrong jets; put the right ones in and problem solved.

I'm also wondering if you can spray either on that seal with it running on it may idle up if it's bad. Not sure however, maybe someone else can say for sure.

I have a john deere liquifire that is doing the same thing. It starts on the first pull, runs great until you get on it and then let off and it dies and wont start. I am pritty sure it is the fuel filter. I am going to clean the tank out really good and just do away with it and see if it fixes it. Sounds like a fuel problem to me also, put the motor under a load and it slowly looses out of gas and cannot get enough to keep it running is what it sounds like.

yes you can spray a little either around the crankseal, and if it idles up it is bad. But usually when crank seals go bad it starts pretty hard. You can check your secondary if it is not allowing it to backshift it would cause a problem when moving or just starting to move. Also if you have brass needle and seats in the carb it will cause an overfuel, or if one of them is sticking it can cause underfueling.

Wrong impression...

I'm horrible at this. I started you down the wrong road. First of the crankshaft seal leak-easy to check. Start the machine and using starter fluid or ether, spray it down around the PTO side of the crank, but keep you hands, fingers, and anything else clear of all the moving parts. And if the RPM goes up, you know you have a leak. But watch the over-spray, because if you get the starter fluid all over, it could be ingested through the airbox?/carbs and increasing the RPMs, thereby giving the same indication as a crank leak.
After hearing the secondary shift theory-great idea, very possible. Fuel, I'm still thinking due to age, it could be the choke cables, but because it only takes a few seconds, check the overflow/vent line to make sure you're not getting vapor drag/intermittent lock from a clogged or blocked line.(Wow, that more run on sentences than the miles I road the last time I was out!)
Take the cap off the fuel tank, locate the end of the vent/overflow line, use your hand to create a seal around the fuel tank inlet, and blow, theoretically pressurizing the fuel tank. With your other hand feel the end of the vent line, can you feel air moving? If you cannot, reverse the process and blow the other way.
Lastly, back to the chokes...., they should only take 1/2 hour or so..